Field of the Invention
The invention relates to a heterostructure comprising at least one carbon nanomembrane on top of at least one carbon layer, a method of manufacture of the heterostructure, and an electronic device, a sensor and a diagnostic device comprising the heterostructure.
Brief Description of the Related Art
Functionalization of pristine carbon layers, e. g. a single layer or a few layers of graphene, allows use of the pristine carbon layers in electronic, mechanical or optical devices, e.g. as electrical transducers in electronic devices, such as, but not limited to, electric field-effect based nanosensors. Stine, R., Mulvaney, S. P., Robinson, J. T., Tamanaha, C. R. & Sheehan, P. E. Fabrication, Optimization, and Use of Graphene Field Effect Sensors. Analytical Chemistry 85, 509-521, (2013); Wu, S. X., He, Q. Y., Tan, C. L., Wang, Y. D. & Zhang, H. Graphene-Based Electrochemical Sensors. Small 9, 1160-1172, (2013). However, the pristine carbon layers have not to date been functionalized in a way which would allow their use in such devices. Kuila, T. et al. Chemical functionalization of graphene and its applications. Progress in Materials Science 57, 1061-1105, (2012); Mao, H. Y. et al. Manipulating the electronic and chemical properties of graphene via molecular functionalization. Progress in Surface Science 88, 132-159, (2013). This is because the pristine carbon layers are chemically relatively inert and are difficult to functionalize via covalent bonding. Pristine graphene is one example of a pristine carbon layer. The graphene consists of exclusively sp2-carbons which are organized in a honeycomb network. A layer of fullerene is another example of a carbon layer.
Structural modifications in the pristine carbon layers can enable the functionalization by covalent bonding, but the electronic, mechanical and optical properties of the modified pristine carbon layer are diminished. Examples of the diminished electronic properties include high electrical charge mobility, strong ambipolar electric field effect, high thermal conductivity. Stine, R., Mulvaney, S. P., Robinson, J. T., Tamanaha, C. R. & Sheehan, P. E. Fabrication, Optimization, and Use of Graphene Field Effect Sensors. Analytical Chemistry 85, 509-521, (2013); Wu, S. X., He, Q. Y., Tan, C. L., Wang, Y. D. & Zhang, H. Graphene-Based Electrochemical Sensors. Small 9, 1160-1172, (2013); Kuila, T. et al. Chemical functionalization of graphene and its applications. Progress in Materials Science 57, 1061-1105, (2012); Mao, H. Y. et al. Manipulating the electronic and chemical properties of graphene via molecular functionalization. Progress in Surface Science 88, 132-159, (2013); and Balandin, A. A. Thermal properties of graphene and nanostructured carbon materials. Nature Materials 10, 569-581, (2011). Examples of the diminished mechanical properties include Young's modulus, internal stress and the tensile strength. Experiments have been performed with graphene as an exemplary carbon layer. Both the covalent bonding to graphene defects, as in oxidized graphene (Dreyer, D. R., Park, S., Bielawski, C. W. & Ruoff, R. S. The chemistry of graphene oxide. Chemical Society Reviews 39, 228-240, (2010)), or to graphene grain boundaries (Steenackers, M. et al. Polymer Brushes on Graphene. Journal of the American Chemical Society 133, 10490-10498, (2011)), and direct bonding to intact benzene rings (Bekyarova, E. et al. Chemical Modification of Epitaxial Graphene: Spontaneous Grafting of Aryl Groups. Journal of the American Chemical Society 131, 1336-1337, (2009)) were studied and have demonstrated the diminished electronic properties. In this respect, non-covalent functionalization of the carbon layers, i.e. via weak van der Waals (vdW) forces, may provide an alternative functionalization, as this non-covalent functionalization does not induce severe changes into the carbon layers, especially a change of the bonding structure. Mao, H. Y. et al. Manipulating the electronic and chemical properties of graphene via molecular functionalization. Progress in Surface Science 88, 132-159, (2013). Thus, the non-covalent functionalization of the carbon layers using the example of graphene with flat polyaromatic molecules like porphyrins (Xu, Y. X. et al. Chemically Converted Graphene Induced Molecular Flattening of 5,10,15,20-Tetrakis(1-methyl-4-pyridinio)porphyrin and Its Application for Optical Detection of Cadmium(II) Ions. Journal of the American Chemical Society 131, 13490-13497, (2009)) has been shown. The adsorbed flat polyaromatic molecules do not disrupt the carbon layer, but the stability of the flat polyaromatic molecules is low and limits use of the functionalized carbon layer in the electronic devices.
Carbon nanomembranes are a novel two-dimensional (2D) carbon-based material with dielectric properties made via electron-/photon-induced crosslinking of aromatic self-assembled monolayers. Turchanin, A. & Gölzhäuser, A. Carbon nanomembranes from self-assembled monolayers: Functional surfaces without bulk. Progress in Surface Science 87, 108-162, (2012); Angelova, P. et al. A Universal Scheme to Convert Aromatic Molecular Monolayers into Functional Carbon Nanomembranes. ACS Nano 7, 6489-6497, (2013). The carbon nanomembranes are mechanically and thermally stable. The terms “carbon nanomembrane” and “cross-linked SAMs” can be used synonymously. The carbon nanomembranes have also been described in U.S. Pat. No. 6,764,758 B1.
Structures comprising the carbon layers may be used in electronic devices, sensors or diagnostic devices. The sensors may also be the diagnostic devices. Conventional diagnostics and diagnostic devices include pathogen cultivation, PCR and enzyme immunoassays, which are all laborious, time consuming and costly methods, requiring large sample volumes, special equipment and trained staff. Mechanical, optical or magnetic sensors used for the diagnostic devices are slow and not very sensitive. Functionalization of sensor surfaces may provide molecular detection specificity in the diagnostic devices. Most capture molecules, however, are not compatible with the materials from which the sensors have been made to date. These materials include silicon, metals and graphene.